Biodegradation Of Dyes Research Articles

Exploring potential bacterial populations for enhanced anthraquinone dyes biodegradation: a critical review.

Anthraquinone dyes, which include an anthraquinone chromophore group, are the second-largest among dye classes, which is often employed in textile manufacturing. A significant number of anthraquinone dyes get into the environment, creating severe pollution since many of these dyes have intricate and stable structures. Currently, microbiological treatment of wastewater is an economically and feasibly viable solution for treating printing and dyeing wastewater, and there are growing reports of biodegradation of anthraquinone dyes. In this review, we outline the current advances in the biodegradation of anthraquinone dyes, summarizes dyes biodegradation by bacterial, fungal, and algae strains, factors influencing dyes biodegradation, current methods in enhancing dyes biodegradation, resuscitation of viable but non-culturable (VBNC) bacteria for better microbial performance, and potentials of VBNC bacteria in degrading dyes. Finally, future directions and important areas for study are given, and such efforts are anticipated to improve the anaerobic degradation process.

Recent advances in biodecolorization and biodegradation of environmental threatening textile finishing dyes.

Organic nature of dyes and their commercially made products are widely utilized in many industries including paper, cosmetics, pharmaceuticals, photography, petroleum as well as in textile manufacturing. The textile industry being the top most consumer of a large variety of dyes during various unit processes operation generates substantial amount of wastewater; hence, nominated as "Major Polluter of Potable Water". The direct discharge of such effluents into environment poses serious threats to the functioning of biotic communities of natural ecosystems. The detection of these synthetic dyes is considered as relatively easy, however, it is extremely difficult to completely eliminate them from wastewater and freshwater ecosystems. Aromatic chemical structure seems to be the main reason behind low biodegradability of these dyes. Currently, various physiochemical and biological methods are employed for their remediation. Among them, microbial degradation has attracted greater attention due to its sustainability, high efficiency, cost effectiveness, and eco-friendly nature. The current review presents recent advances in biodegradation of industrial dyes towards a sustainable and tangible technological innovative solutions as an alternative to existing conventional physicochemical treatment processes.

Impact of immobilized algae and its consortium in biodegradation of the textile dyes

In biological engineering, cell immobilization is a modern technique for immobilizing free cells in a small space. Disintegration and elimination of azo dyes [Reactive Orange 122 (orange 2RL) and Reactive Red 194 (Reactive Red M-2BF)] were investigated by using Chlorococcum sp. and Chlorococcum sp. mixed with Scenedesmus obliquus, respectively. After 7 days of incubation, the maximum decolorization was spotted at 40 ppm for Reactive Orange 122 and 20 ppm for Reactive Red 194 by Chlorococcum sp. and Chlorococcum sp. mixed with S. obliquus, respectively. The findings revealed that the best decolorization activity was found at pH 11 and 25 °C under aeration conditions. BG11 was considered the best medium for azo dye decolorization with a high decolorization percentage. Additionally, different concentrations of nitrogen and phosphorus show the high activity of decolorization of both dyes. Referring to vitamins (thiamin and Ascorbic acid), all studied concentrations showed high decolorization activity with immobilized Chlorococcum sp. mixed with S. obliquus; however, different concentrations (20, 40, and 60 mg/l) of thiamin showed completely decolorization of Reactive Red 194 after 3 days, and 60 mg/l of ascorbic acid showed completely decolorization of Reactive Orange 122 after 5 days of inoculation. FT-IR and GC-Ms analysis for azo dyes after and before treatment with Immobilization of Chlorococcum sp. and Chlorococcum sp. mixed with Scenedesmus obliquus were detected. Novelty statement: The natural carrier algae and its consortium combined with a suitable immobilization technique were considered in this study, which is non-toxic, enhanced their bioremediation potential for dyes, and allowed multiple uses of biocatalysts. The novel use of the immobilization and its consortium of algae on the degradation efficiency of azo dyes and studying the effect of physicochemical conditions on decolorization and degradation of azo dyes. Application of immobilization techniques using microalgae could be excellent bioremediation of wastewaters.

Dyes Biodegradation in the Presence of Hexavalent Chromium by Streptomyces sp. KY75: a Novel Heavy Metal Resistant Strain Isolated in Algeria

Dyes Biodegradation in the Presence of Hexavalent Chromium by Streptomyces sp. KY75: a Novel Heavy Metal Resistant Strain Isolated in Algeria

Microbial Remediation of Textile Dye Acid Orange by a Novel Bacterial Consortium SPB92

Textile effluent generated during the dyeing process of textiles is a huge supplier to water toxicity all over the world. Textile dyes are the main toxic component found in the effluent sample which is difficult to treat. A bacterial consortium capable of decolourizing and degrading the textile dye acid orange is reported in this research article. The bacterial consortium was identified by 16 S rDNA sequence and phenotypic characteristics. It is composed of four strains i.e., Pseudomonas stutzeri (MW219251), Bacillus tequilensis (MW110471), Bacillus flexus (MW131645), Kocuria rosea (MW132411). The consortium was able to cause decolorization of azo dye acid orange (30 mg/L) in 23 h, when kept under static laboratory conditions. The optimal pH and temperature for color removal were pH 7.5 and 32°C, respectively. The decolorization of dye before and after was checked by UV-Visible absorption spectra. This gives evidence that decolorization was caused due to biodegradation. This was further assured by studying the reduction of biological oxygen demand (BOD5 (96%), chemical oxygen demand (COD) (79%), and TOC (total organic carbon) (54%) of the bacterial-treated water sample. The Fourier transform-infrared spectroscopy (FT-IR) spectroscopy and gas chromatography-mass spectroscopy (GC-MS) results confirmed the mineralization of the dye. The results indicate the effectiveness of the bacterial consortium SPB92 in the biodegradation of acid orange dye. This demonstrates that the consortium has immense potential and will serve as an important contributor to the treatment of textile wastewater.

Biodecolourization of Azo Dye under Extreme Environmental Conditions via Klebsiella quasipneumoniae GT7: Mechanism and Efficiency

Introduction: Biodegradation of azo dyes under harsh environmental conditions has been of great interest for the treatment of colored effluents. The present study aims to evaluate Klebsiella quasipneumoniae GT7 for degrading azo dye Carmoisine under extreme pH conditions and high salinity.
 Materials and Methods: The growth profiles of bacteria were compared under different conditions of salinity and pH, using the optical density and viability measurements. Kinetic patterns of decolourization by GT7 were investigated under different concentrations of NaCl and/or pH, through the spectrophotometry method. Moreover, thin layer chromatography (TLC) was used to evaluate the biotransformation of Carmoisine into aromatic amines. Scanning electron microscopy (SEM) was carried out to analyze any morphological changes in bacteria under stress conditions.
 Results: GT7 showed OD-based growth and sustainable viability under [NaCl] ≤ 15% and/or initial pH between 3-11. The viable but nonculturable (VBNC) state explained the bacteria's survival under attenuated growth due to bacterial inefficiency to maintain cytoplasmic osmotic balance, vital turgor pressure, and pH homeostasis. Biodecolourization was accomplished during 48h, where Carmoisine was 50mg/l, [NaCl] ≤ 20%, and/or initial was pH 5-11. TLC, OD600nm and pH measurements as well as visual observation of bacterial pellets at the end of the decolourization confirmed biodegradation as the dominant mechanism, except for pH 3, where dye was removed via adsorption to the cell surface. SEM showed morphological alteration of GT7 from rod to coccoid shape as an approach to resist the harsh conditions ratio.
 Conclusion: GT7 is shown as an efficient strain for azo dye degradation in harsh environmental conditions.

Lignin peroxidase from the white-rot fungus Lentinus squarrosulus MPN12 and its application in the biodegradation of synthetic dyes and lignin

Lignin peroxidase (LiP), which has been studied extensively in white-rot basidiomycetes and their potential to degrade dyes from textile wastewater, plays a role in the biodegradation of lignin from pulp and paper industry wastewater, as well as agricultural waste. Lignin peroxidase (LsLiP) was successfully purified from the newly isolated Lentinus squarrosulus MPN12 with a 47.1-fold purification and a 15.7% yield. After 48 h-incubation, LsLiP was able to decolorize all tested dyes up to 92% for Acid Blue 62 (NY3), followed by Porocion Brilliant blue HGR (PB, 73.5%), Acid Blue 281 (NY5, 70.5%), Acid Blue 113 (IN13, 61%), Acid red 266 (NY7, 56%), and 34.5% for Acid red 299 (NY1), compared to the negative control with the heat-denatured enzyme. The biodegradation potential of LsLiP was further suggested by the change of lignin structure based on Fourier transform infrared (FTIR) analyses. Lignin structure was noticeably changed before and after LsLiP treatment, especially in the fingerprint regions (1600 to 1000 cm-1) and 2930 cm-1 corresponding to the stretching vibrations of various groups in lignin. Thus, LsLiP has potential application in both enzyme-based decolorization of synthetic dyes and lignin biodegradation.

Biodegradation of harmful industrial dyes by an extra-cellular bacterial peroxidase

Nowadays the treatment of environmental pollutants such as synthetic dyes (used in multiple industries such as paper, textile, food, plastic and pharmaceutical) has received much attention, especially for biotechnological treatments using both native and artificial enzymes. In this context, many enzymes have been reported to efficiently perform dye degradation. Peroxidase is one such enzyme, which causes dye degradation either by precipitation of chemical structure of aromatic dyes or by opening up their aromatic ring structure. In the present study an extra-cellular peroxidase extracted from a bacterial strain Bacillus sp. F31 JX984444.1 was tested for its capability to decolorize 16 different dyes used in various industries. Out of 16 different textile dyes the Bacillus sp. peroxidase efficiently decolorized 5 dyes out of which 4 triphenyl methane dyes (Basic Fuchsin (BF), Rhodamine B (RB), Coomassie Brilliant Blue (CBBG) and Malachite Green (MG) showed decolorization up to 95.5%, 70.8%, 70% and 40%, respectively, while a polymeric heterocyclic dye Methylene Blue (MB) showed 66.2% decolorization. These 5 dyes were studied to further enhance their decolorization by peroxidase after purification by optimizing different reaction conditions (temperature, time, enzyme concentration, buffer pH, dye concentration and effect of various salt ions, H2O2 concentration). This study indicates that the extracellular peroxidase (purified) from Bacillus sp. can be used as a useful tool for the treatment (degradation/decolorization) of industrial effluents contaminated with harmful industrial dyes.

Towards passive bioremediation of dye-bearing effluents using hydrous ferric oxide wastes: Mechanisms, products and microbiology

A novel, circular economy-inspired approach for the “passive” (non-powered and reagent-free) treatment of dye-bearing effluent is presented. The treatment utilises the biogeochemical interaction of dye-bearing wastewater with hydrous ferric oxide (HFO) bearing sludges. The work presented demonstrates for the first time the reuse of HFO-rich waste sludges from potable water and mine water treatment. The waste was used directly without modification or reagent addition, as media/substrate in simple flow-through reactors for the decolourisation and biodegradation of methyl orange (MO) and mixed dyes textile effluent. Three phases of exploratory proof of concept work were undertaken. Columns containing HFO sludges were challenged with solution of MO, and MO amended with glycerol (Phase I), MO in a synthetic textile effluent recipe (Phase II), and real mixed textile effluent containing a mixture of dyes (Phase III). After an initial lag period extensive decolourisation of dye was observed in all cases at rates comparable with pure strains and engineered bioreactor processes, with evidence of biodegradation beyond simple cleavage of the mono azo chromophore and mineralisation. The microbiology of the initial sludge samples in both cases exhibited a diverse range of iron oxidising and reducing bacteria. However, post experiment the microbiology of sludge evolved from being dominated by Proteobacteria to being dominated by Firmicutes. Distinct changes in the microbial community structure were observed in post-treatment MWTS and WTWS where genera capable of iron and sulphate reduction and/or aromatic amine degradation were identified. Average nitrogen removal rates for the columns ranged from 27.8 to 194 g/m3/day which is higher than engineered sequential anaerobic-aerobic bioreactor. Postulated mechanisms for the fast anaerobic decolourisation, biodegradation, and mineralisation of the dyes (as well nitrogen transformations) include various direct and indirect enzymatic and metabolic reactions, as well as reductive attack by continuously regenerated reductants such as Fe(II), HFO bound Fe(II), FeS, and HS−. The ability of iron reducers to degrade aromatic rings is also considered important in the further biodegradation and complete mineralisation of organic carbon. The study reveals that abundant and ubiquitous HFO-rich waste sludges, can be used without amendment, as a substrate in simple flow-through bioremediation system for the decolourisation and partial biodegradation of dyes in textile effluent.

A dye-methylene blue (MB)-degraded by hydrodynamic cavitation (HC) and combined with other oxidants

As a kind of AOPs, hydrodynamic cavitation (HC) has the characteristics of energy savings and easy amplification. It is of great significance to study the degradation of dye molecules with HC, due to the toxicity, chroma and difficult biodegradation of dyes. In the present work, the HC treatment of methylene blue (MB) was investigated, and the effects of inlet pressure, solution pH, and initial concentration on the degradation of MB dye were explored. The maximum degradation rate of MB was obtained at 0.3 MPa, pH = 2, and an initial concentration of 10 mg/L. The combination of Na2S2O8 or O3 with HC were also conducted to explore their synergistic effect. The results indicated that the degradation performance of introducing ozone is better that of adding Na2S2O8. When the amount of O3 gas was 0.12 g/h, the MB degradation rate was over 99%, and the synergy index was 3.58. The intermediate products in the MB disintegration process were detected based on LC-MS, and the reaction mechanism and path of MB were proposed.

Decolorization and toxicity evaluation of simulated textile effluent via natural microbial consortia in attached growth reactors

Textile wastewater is heterogeneous in nature with multiple types of dyes and other chemicals. Considering this point, attached growth bioreactors were constructed, using sludge (SD), alkalophilic (AK), and thermophilic (TH) bacterial consortia to develop an effective dye biodegradation system. Simulated dye wastewater, containing a 50 ppm mixture of three reactive azo dyes, viz. Reactive Blue (RB 221), Reactive Yellow (RY 145), and Reactive Red (RR 195) were treated under batch mode operation for up to 192 h. Overall, the color removal efficiency of the reactors varied from 85 to 94 % in 192 h. The thermophilic consortium achieved maximum decolorization (93.5 %), operated at 50 °C, while the alkalophilic consortium attained maximum COD reduction (93.0 %). Nitrites and nitrates were reduced to (14.7 – 79.3) – (84 – 239.4) mg/L, while sulfates ranged from 624.7 – 1003 mg/L. In addition, scanning electron microscopy (SEM) analysis revealed the biofilm community structure, indicating diverse bacterial interactions among each consortium. The biodegradation of dyes was further confirmed through Fourier-transform infrared spectroscopy (FTIR). Phytotoxicity and cytotoxicity analyses revealed that the dye mixture became non-toxic after treatment. This study outlines that natural microbial consortia are efficient dye decolorizers and confers the possibility of using microbial consortia for upscale biological treatment of dyeing effluents.

Biodegradation of synthetic dyes by free and cross-linked peroxidase in microfluidic reactor

This paper aims to reduce the gap between intensified innovative process designs and the application of enzyme technologies at an industrial scale that often take full advantage of microreactor systems. Soybean and potato processing waste was used as the source of peroxidase in both the free and immobilized form for the biodegradation of the Acid Violet 109 anthraquinone dye (AV109) in a PTFE (polytetrafluoroethylene) microreactor which is 0.5 mm in diameter and 6 m in length. High biodegradation efficiencies of 95 and 76% were achieved by soybean and potato peroxidase respectively after 3 min of residence in the microreactor, with a noticeable lack of hydrogen peroxide inhibition. The reactor’s design, with regard to its diameter and length, significantly affected the biodegradation efficiency. The polymer membrane formation by the cross-linking approach with oxidized pectin and soybean or potato peel peroxidase on the inner PTFE wall was SEM confirmed. The cross-linking efficiency with oxidized pectin of both peroxidases is inversely correlated with the activity, hence the highest recorded activity of immobilized peroxidase was 11 and 19 μ mol/min of soybean and potato peroxidase, respectively, at an initial pectin concentration of 0.05%. A promising reusability for AV109 biodegradation in the microreactor with immobilized soybean and potato peroxidase was confirmed, since the immobilized peroxidases retained 65 and 35% of the initial activity after the tenth cycle, respectively. The LC–MS and GC–MS techniques confirmed the biodegradation of the AV 109 dye, and the intermediates with a lower molecular weight were separated and identified. • Soybean and potato processing waste was used as the source of peroxidase. • Microreactor was used for the biodegradation of anthraquinone dye. • Biodegradation efficiency of 95% and 76% was achieved for both peroxidase. • The peroxidases were immobilized on the inner microreactor surface. • The immobilized enzymes retained 65 and 35% of the activity after tenth cycle.

Biodegradation of methyl red dye by a novel actinobacterium Zhihengliuella sp. ISTPL4: Kinetic studies, isotherm and biodegradation pathway

Among azo dyes, methyl red dye is mutagenic and its persistence causes serious impacts on the environment and human health. The current study is the first report of methyl red dye degradation by an actinobacterium, Zhihengliuella sp. ISTPL4. Strain showed 98.87% of 500 mg/L methyl red dye degradation within 12 h. Optimization of the efficient decolorization by the strain, Quadratic regression model analysis was done by using R software. The kinetic studies revealed the biosorption of dye and explained by Freundlich isotherm model where maximum adsorption was observed (0.99) followed by a pseudo second order reaction. N,N -dimethyl-p-phenylaminediamine (DMPD), and 2-aminobenzoic acid (2-ABA) were detected as key metabolites. Whole genome sequencing analysis showed the presence of azoreductase enzyme. FTIR analysis showed the reductive cleavage of the methyl red azo bond. Furthermore, the degradation pathway of methyl red has been proposed. With these results, we propose a novel application of Zhihengliuella sp. ISTPL4 in methyl red dye degradation at higher concentration.

Ameliorative biodegradation of hazardous textile industrial wastewater dyes by potential microalgal sp.

Ameliorative biodegradation of hazardous textile industrial wastewater dyes by potential microalgal sp.

Biodegradation of Azo Dye by Bacterial Species Isolated from Dye Contaminated Area of Jetpur, Gujarat

The varieties of synthetic azo dyes are widely used in textile industries to generate range of color tones in the textile and paper industries. Such textile dyes are toxic for the animals, birds and human along with environment. It is needful to remove those dyes from the effluent. The degradation of such dyes is accompanied by the involvement of dye degradating microorganisms. The purpose of this research is to isolate, identify, and screen bacterial species capable of decolorizing reactive pink, congo red, and malachite green. Soil and water samples were collected from the dye contaminated area of Jetpur, Gujarat, India. Dye degradating bacteria were isolated and selected through primary and secondary screening. The effect of yeast extract amount on the dye degradation properties of bacteria was examined using a visible spectrophotometer.
 After secondary screening MD2, MD8, MD20, MD31, MD33 and MD34 were selected for further analysis. All isolated are able to degrade reactive pink, congo red, and malachite green after 120hrs of incubation at a 4mgl-1 concentration of yeast extract. Dye degradation remains constant for 4 mgl-1 and 2 mgl-1 but gets reduced in 1 mgl-1 of yeast extract concentration. Wheat germination rate in control was 65% compared to 96%, 88%, and 85% in MD2, MD8, MD20 respectively. Sorghum germination rate in control was 62% while in isolates no MD31, MD33, MD34 were 96%, 87%, 83% and 65%.

Discerning the biodegradation of binary dyes in microbial fuel cell: Interactive effects of dyes, electron transport behaviour, autocatalytic mechanism, and degradation pathways

This research presented the first attempt to investigate the effect of biodegradation of binary Acid Orange 7 (AO7) and Reactive Green 19 (RG19) on the performances of wastewater treatment and bioelectricity generation, using anti-gravity flow microbial fuel cell (AGF-MFC) system. The influences of initial dye concentration, substrate loading, sulphate concentration and application of quinones on system performances were comprehensively evaluated. The decolourization efficiencies of AO7 were higher than RG19 in binary solutions, at every tested concentrations. The addition of higher concentration of RG19 in binary solution was also found to have increased the overall performances of MFC, owing to electron mediating characteristics of its decolourized intermediates. However, the power density declined with the addition in dye concentration. Further increase of substrate loading by 3-folds (2.43 g/L) improved the decolourization efficiency approximately by 7%, but deteriorated power performance by 42%, to 63.40 ± 0.07 mW/m2. Increasing sulphate concentration from 20 to 400 mg/L had resulted in a high decolourization extent of binary dyes ascribed to sulphide-mediated dye degradation, whereas the power generation was reduced. The increase of sulphate to 800 mg/L led to decrease in decolourization and power density of the system. These outcomes deciphered the competitions of electrons between different electron acceptors in the anodic compartment. Moreover, the autocatalytic mechanism of RG19 decolourized intermediates, 1-amino-2-naphthol-3,6-disulphonate (1A2N36S) as electronophore was thoroughly unearthed. Detailed degradation pathways of dyes were proposed based on UV-Visible spectra and gas chromatograph-mass spectrometer (GC-MS) analyses.

Biological Removal of Dyes from Wastewater: A Review of Its Efficiency and Advances

Biological removal of dyes has been advocated due to its simplicity, cost-effectiveness, and low operational requirements in comparison to physicochemical methods of treating dye effluents. This paper aims to compare the efficiency of biological removal of dyes using bacteria, algae, and fungi, including yeasts, besides presenting the recent advances in the field. This paper reviewed scholarly articles published mainly between 2010 and 2021. It found bacteria could degrade a myriad of dyes. Different bacteria could degrade the same dye with different efficiencies. Similarly, one bacterial species could degrade multiple dyes with varying efficiencies. Though regarded as having a faster rate of dye biodegradation than fungi, this review finds bacteria to have comparable performance to fungi in decolorizing dyes, and it is worth mentioning that a few yeast species were reported to have very high efficiency in decolorizing dyes. Mixed bacteria or bacteria-fungus cultures were generally found to have better dye-decolorizing efficiency than pure cultures. Algae have relatively lower efficiency than bacteria and fungi in decolorizing dyes and might require longer contact time. New advances such as genetic engineering as well as immobilization of microorganisms and enzymes could improve the efficiency of dye biodegradation. Nonetheless, before biological removal of dyes can be feasibly applied, there are limitations that need to be overcome. Major limitations include the inconsistent performance of various organisms in decolorizing dyes; the complexity of optimization; inability to completely decolorize dyes; potential formation of toxic by-products upon decolorization of dyes; safety concerns of immobilization materials; and cost and technical feasibility of biological removal of dyes. This review has the significance of highlighting the important bottlenecks of the current biological dye removal technology, which could pave the way for breakthroughs in this domain of research.

Nanomaterials: An alternative source for biodegradation of toxic dyes

Environment contamination is a colossal worriment across the world, owing to its detrimental and negative impact on health and ecological systems. Dyes are one of the synthetic organic chemicals that are utilised in a variety of fields, including textiles. As a result, throughout one's production and subsequently in fibre colouring, these are becoming frequent industry-contributed contaminants. Increasing globalisation of international market has presented a problem to textile sector in terms of consistency and production. Textile processors' primary concern, as the highly competitive environment and environmental standards grow more severe is about being mindful of the grade of goods and even non-toxicity of their production processes. There seems to be an immediate necessity to look for methods and technologies which are useful in removing dye colours. Even though each has benefits and weaknesses, many physical, chemical, and biological approaches were explored and used with the application being dependent on the effluent properties, technical feasibility, and cost. Several remediation technologies are already developed, but they seem to be ineffective at removing dyes completely. There is a fast growth of nanoparticles applications in the past few years which has opened up newer, innovating, highly efficient, and low-cost dyes remediation systems. Nanomaterials with large surface areas change surface characteristics and distinctive electron conducting capabilities which make them ideal candidate for the treatment of wastewater that contains dyes. In this review, we have highlighted not only the role of nanotechnology in dye remediation processes but also different types of nanomaterials that can be used for the remediation of dyes.

Biodegradation of Reactive Yellow-145 azo dye using bacterial consortium: A deterministic analysis based on degradable Metabolite, phytotoxicity and genotoxicity study

Azo dyes are used at larger-scale as coloring agent in the textile industry. It generates a huge amount of dye containing wastewater and its toxicity threatens all kinds of life and also impacts human beings. At present, more impetus is being given to the biological treatment of dye effluent because of its azoreductase enzyme action to break down azo bond which leads to decolorization and degradation of dye. Bacterial consortium of E. asburiae and E. cloacae (1:1 ratio) was used for degradation and decolorization of Reactive Yellow-145 (RY-145) dye. The optimization of dye concentration, temperature, pH, and media has been carried out to determine the conditions required for maximum degradation and decolorization. The mixed consortium (10%) has shown 98.78% decolorization of RY-145 dye under static condition at 500 mgL−1 concentration, 35 °C and pH 7.0 at 12 h contact period. FTIR analysis showed formation of new functional groups in the treated dye, such as O–H stretch at 1361 cm−1, C–H stretch at 890 cm−1, N–H stretch at 1598 cm−1 and aromatic C–H at 671 cm−1 revealing degradation of dye. Biodegraded metabolites of RY-145 dye were identified through GC-MS analysis that includes 2-Cyclohexen-1-ol, 5-Nitroso-2, 4, 6-triaminopyrimidine, Octahydroquinoline-9-hydroxyperoxide, Tetramethyl-2-hexadecen-1-ol, 9-Octadecanoic acid, methyl ester and Hexadecanoic acid, methyl ester, respectively which have industrial applications. Cyclohexane was used in gasoline and adhesive while Octahydroquinoline-9-hydroxyperoxide and 5-Nitroso-2, 4, 6-triaminopyrimidine were used in manufacturing drugs. Tetramethyl-2-hexadecen-1-ol, 9-Octadecanoic acid, methyl ester and Hexadecanoic acid, methyl ester are antimicrobial and antioxidant. Phytotoxicity test also showed non-toxic effects of treated dye on germination of Cicer arietinum and Vigna radiata seeds. Similarly, genotoxicity study indicated less toxic effects of biodegraded dye products on Mitotic index (MI) and cell division of Allium cepa.

Enhanced Bioremediation Potential of Shewanella decolorationis RNA Polymerase Mutants and Evidence for Novel Azo Dye Biodegradation Pathways.

Bioremediation has been considered as a promising method for recovering chemical polluted environments. Here Shewanella decolorationis strain Ni1-3 showed versatile abilities in bioremediation. To improve the bioremediation activity, RNA polymerase (RNAP) mutations of strain Ni1-3 were screened. Eleven mutants were obtained, of which mutant #40 showed enhanced Amaranth (AMR) degradation capacity, while mutant #21 showed defected capacity in AMR degradation but greatly enhanced capacity in cathodic metal leaching which is three to four times faster than that of the wild-type (WT) strain Ni1-3, suggesting that different pathways were involved in these two processes. Transcriptional profiling and gene co-expression networks between the mutants (i.e., #40 and #22) and the WT strain disclosed that the non-CymA-Mtr but cytochrome b- and flavin-oxidoreductase-dominated azo dye degradation pathways existed in S. decolorationis, which involved key proteins TorC, TorA, YceJ, YceI, Sye4, etc. Furthermore, the involvement of TorA was verified by trimethylamine N-oxide reduction and molybdenum enzyme inhibitory experiments. This study clearly demonstrates that RNAP mutations are effective to screen active microbial candidates in bioremediation. Meanwhile, by clarifying the novel gene co-expression network of extracellular electron transfer pathways, this study provides new insights in azo dye degradation and broadens the application of Shewanella spp. in bioremediation as well.